The present invention relates generally to optical systems, and more particularly to optical analog-to-digital converters.
Rapid advances in technology, particularly greater processing speeds, increased channel bandwidths and improved transmission reliability, have resulted in a steadily growing focus on the optical domain and the vast potential therein. Being a relatively new area compared with electrical, radio frequency (RF)-based processing, existing optical technology available in many areas is immature at best. In particular, the promise of high-speed, large-bandwidth processing advances with digital optics has been hampered by the lack of or the immaturity of many basic technologies taken for granted in the RF domain.
The optical analog-to-digital converter is one such technology where technological advances are desired. In particular, current digital optical systems rely on digitization in the electrical/RF domain, requiring slow, lossy, noisy conversions back and forth between the optical and RF domains. Furthermore, present optical analog-to-digital converters utilize a "downward-folding" successive approximation approach to test the sampled analog signal against a specific threshold. If the sample is below threshold, the bit is set to "low" and the sample is passed directly to the next bit stage. If the signal amplitude is above the threshold, the bit is set to "high" and the system goes about reducing the sample amplitude by the threshold value before passing it on to the next bit stage. Each successive stage tests the sample against thresholds growing closer and closer to zero. The algorithm for such a converter is difficult to implement in an optical regime because simple, robust methods of subtracting optical signals from one another have not been adequately developed.
What is needed therefore is a device which would convert an optical analog signal to an optical digital signal with little or no reliance on RF technology, thereby reducing system complexity and allowing for high speed, large bandwidth processing advances.